Support is requested for a Keystone Symposia meeting entitled Molecular Cell Biology of Macrophages in Human Diseases, organized by Frederic Geissmann, Judith E. Allen and Christopher K. Glass. The meeting will be held in Santa Fe, New Mexico from February 9-14, 2014. In recent years, studies of the development, genetics, and molecular cell biology of macrophages have advanced our understanding of their major role in health and diseases. Many questions remain to be answered with respect to mechanisms that control macrophage development and function, particularly in the context of human genetic heterogeneity. Recent discoveries have also revealed greater heterogeneity in macrophage function and origins than previously appreciated. Answering these questions will have major implications for human health and disease. To help meet this challenge, the Keystone Symposia meeting on Molecular Cell Biology of Macrophages in Human Diseases will bring together leading and upcoming scientists in immunology, infectious diseases, metabolism, molecular biology and genetics, development, cancer, and cell migration with a common interest in macrophages and their roles in human diseases. In addition to the regular sessions, three workshops will provide a platform to discuss the findings of junior scientists (selected from the submitted abstracts). These workshops will additionally help to focus the meeting on some of the fastest moving areas of macrophage biology.